1. Field of the Invention
The present invention relates to a display and more particularly, to a color electrophoretic display (electronic paper) in which red color electronic ink, green color electronic ink, and blue color electronic ink are formed using a photoresist sheet and an exposure process and are sequentially arranged, and a method of manufacturing the same.
2. Discussion of Related Art
An electrophoresis phenomenon means a phenomenon that charged particles move when an electric field is applied between both electrodes. When the electrophoresis occurs within a dielectric fluid, the charged particles move at a velocity determined by a viscous drag, charges, dielectric properties of the fluid, and a magnitude of the applied electric field.
An electrophoretic display using the above-described electrophoresis phenomenon has most superior properties including a high resolution, a wide viewing angle, a bright white background like the existing paper and ink among display media, and can advantageously implemented on any substrates such as plastic, metal, sheet, and so forth. Such an electrophoretic display can be applied to an e-newspaper, an e-magazine, an e-book replacing the existing newspaper, magazine, book or the like, and an information display media of a mobile communication device such as a cellular phone, a personal digital assistant (PDA), or the like.
The electrophoretic display determines a color using particles having one or more colors suspended in a dielectric fluid. That is, when an electric field is applied to particles having one or more colors, two kinds of particles having an opposite polarity to each other move toward an electrode having a polarity opposite to a polarity of the applied electric field. As a result, a change in color can visually viewed.
The electrophoretic display has bistability. That is, it maintains the color prior to removal of the electric field is removed even after the applied electric field is removed. For these advantages, many researches have been conducted since Ota has first proposed a reflective display using the electrophoresis phenomenon in the early 1970s (see I. Ota, J. Ohnishi, and M. Yoshiyama, Proc. IEEE 61, 1973 p 832). However, the electrophoretic display proposed by Ota had problems in stability. That is, density of charged particles within a fluid is made to be the same as that of the fluid to prevent the charged particles from being precipitated. However, clustering and agglomeration of particles occurred due to the suspension instability according to a time, which were brought to a severe difficulty in being put into a commercial use (see P. Murau and B. Singer, J. Appl. Phys. 49, 1978 p 4820). These problems were not overcome until the late 1990s from 1980s so that the researches could not significantly advance.
E-ink branched from the MIT Media Lab in 1996 has solved these problems using a microcapsule to some extent (see U.S. Pat. Nos. 6,262,706, 6,262,833, and 5,916,804). The microcapsule can contribute to spatially separate particles so that clustering and agglomeration are reduced. An electrophoretic display using the microcapsule will be briefly described below.
FIGS. 1A and 1B illustrate an electrophoretic display using a microcapsule in accordance with the related art. As shown in FIG. 1A, the electrophoretic display has a lower electrode 13 and a lower electrode protective layer 15 on a lower layer 11. A microcapsule 17 is formed on the lower electrode protective layer 15. The microcapsule 17 is configured to have a transparent fluid 19, white particles 21 having positive charges, and black particles 23 having negative charges. The lower electrode protective layer 15 acts to protect the lower electrode 13 and separate the lower electrode 13 from the microcapsule 17. And an upper electrode protective layer 24 and an upper electrode 25 are formed on the microcapsule 17. When an electric field is applied to the upper electrode 25 and the lower electrode 13, particles within the microcapsule 17 are moved by the electrophoresis phenomenon. The upper electrode protective layer 24 acts to protect the upper electrode 25 and separate the upper electrode 25 from the microcapsule 17. A transparent upper layer 27 is formed on the upper electrode 25. In the above-described structure, an electric field is not applied between the lower electrode 13 and the upper electrode 25. Accordingly, particles 21 and 23 are suspended within the fluid 19.
As shown in FIG. 1B, when an electric field is applied between the lower electrode 13 and the upper electrode 25, charged particles within the microcapsule 17 are moved toward an electrode having a polarity opposite to the polarity of the charged particles. The movement of the charged particles allows a change in color to be visually viewed.
However, in the case of the electrophoretic display using the above-described microcapsule, a monochrome is displayed using electronic inks of black and white colors, or a color is displayed using a color filter, and researches on the electrophoretic display using color electronic inks are still in progress.